FIG. 1 is a cross-section schematic of a conventional containment building 10 cross section. Although containment 10 is shown in FIG. 1 having components and characteristics of an Economic Simplified Boiling Water Reactor (ESBWR), it is understood that components described therein are usable with other plant configurations. As shown in FIG. 1, containment 10 may include a gravity-driven coolant system (GDCS) 15, which may be a large, water-filled tank used to cool a reactor vessel in the event of a loss of primary coolant. A suppression pool 16 may be within containment 10 and used to condense steam from the reactor vessel and relieve pressure in the event of an accident. Several Passive Containment Cooling System (PCCS) condensers 50 are arranged in a PCCS pool 20, outside of containment 10. The PCCS condensers 50 remove additional heat and condense steam within containment 10 during a loss of coolant accident within the containment 10.
PCCS condensers 50 include an inlet 51 within containment 10 that receives steam and noncondensable gasses that may be released into containment 10 during a severe accident. The steam is formed from boiling coolant in the reactor, and the noncondensable gasses, such as O2 and H2, accumulate within the reactor and containment 10 during operation of the nuclear plant from radiation and chemical release. The steam and noncondensable gasses pass through inlet 51 of PCCS condenser 50 into branched pipes and vertical tubes 52, which are submerged in the PCCS pool 20. Heat from the steam and noncondensable gasses is transferred from vertical tubes 52 to PCCS pool 20, and steam within vertical tubes 52 condenses into water. Lower headers 53 collect the condensed water and noncondensable gasses in the PCCS condenser 50.
From lower header 53, the condensed water is driven by gravity and a pressure differential downward through an annular duct 54, which includes two concentric pipes that provide an inner and outer passage in annular duct 54. Condensed water flows through the outer pipe of annular duct 54 into a shared drain line 57, which drains the condensed water into GDCS pool 15. From the lower header 53, noncondensable gasses flow downward through the inner passage 54a (FIG. 2) in annular duct 54 into vent line 58, which terminates at a sparger 59 in suppression pool 16. A fan 30 may be connected to the vent line 58 to enhance noncondensable flow out of PCCS condensers 50.
The lower header 53 includes a drain manifold 55 that separates condensed water and noncondensable gasses into the outer and inner passages, respectively, of the annular duct 54. FIG. 2 is an illustration of conventional drain manifold 55. As shown in FIG. 2, drain manifold 55 includes a vent hood/drip hood 75 that diverts condensed water flowing downward onto the drip hood 75 to either side of drain manifold 55. Several compression wave baffles 65 brace and secure drain manifold 55 in lower header 53. Noncondensable gasses are permitted to flow up into drip hood 75 and into inner passage 54a of annular duct 54, while the diverted condensed water flows into the outer passage about the edges of annular duct 54. In this way, the water may flow back into GDCS pool 15 for use as reactor coolant without any noncondensable gasses causing blocked or reverse flow.